The present invention generally relates to a method of and an apparatus for optically and automatically detecting defects of a joint portion of an elastic-member sheet such as a tire tube or the like.
Conventionally, the splicing defect of a joint portion such as a tire tube joint is inspected by such a method as shown in FIG. 5(b). A defective splicing location 32, which is caused by talc biting, staggered splicing cure or the like in the joint portion 33 of a tire tube 31 of FIG. 5(a) comes out as being a dent in a pull condition. Both sides of the defective splicing location 32 are grasped by a sheet tension machine (not shown), so that the defective splicing location is dented through the pulling operation until the tire tube becomes approximately two through three times as long as before as shown by an arrow A in FIG. 5(b). An operator visually observes the upper surface 33a of the joint portion 33 directly and the reverse face 33b of the joint portion 33 directly through a mirror so as to judge whether or not the dent is defective in accordance with the experimental judgement of the operator.
However, the conventional method of inspecting the defects does not have universal validity in inspection, because the quality of the joint portion is judged by the experiment simply through the visual observation of the operator. The judgement reference is not quantitative, thus being vague under the control of personal subjectivity. Furthermore, because of the human visual inspection, longer time is ineffectively required for the inspection, and some oversights of the defective locations are unavoidable by mistake.